DESCRIPTION

The
getprotoent_r(),
getprotobyname_r(),
and
getprotobynumber_r()
functions are the reentrant equivalents of, respectively,
getprotoent(3),
getprotobyname(3),
and
getprotobynumber(3).
They differ in the way that the
protoent
structure is returned,
and in the function calling signature and return value.
This manual page describes just the differences from
the nonreentrant functions.

Instead of returning a pointer to a statically allocated
protoent
structure as the function result,
these functions copy the structure into the location pointed to by
result_buf.

The
buf
array is used to store the string fields pointed to by the returned
protoent
structure.
(The nonreentrant functions allocate these strings in static storage.)
The size of this array is specified in
buflen.
If
buf
is too small, the call fails with the error
ERANGE,
and the caller must try again with a larger buffer.
(A buffer of length 1024 bytes should be sufficient for most applications.)

If the function call successfully obtains a protocol record, then
*result
is set pointing to
result_buf;
otherwise,
*result
is set to NULL.

RETURN VALUE

On success, these functions return 0.
On error, they return one of the positive error numbers listed in ERRORS.

On error, record not found
(getprotobyname_r(),
getprotobynumber_r()),
or end of input
(getprotoent_r())
result
is set to NULL.

ERRORS

ENOENT

(getprotoent_r())
No more records in database.

ERANGE

buf
is too small.
Try again with a larger buffer
(and increased
buflen).

ATTRIBUTES

For an explanation of the terms used in this section, see
attributes(7).

Interface

Attribute

Value

getprotoent_r(),
getprotobyname_r(),
getprotobynumber_r()

Thread safety

MT-Safe locale

CONFORMING TO

These functions are GNU extensions.
Functions with similar names exist on some other systems,
though typically with different calling signatures.

EXAMPLE

The program below uses
getprotobyname_r()
to retrieve the protocol record for the protocol named
in its first command-line argument.
If a second (integer) command-line argument is supplied,
it is used as the initial value for
buflen;
if
getprotobyname_r()
fails with the error
ERANGE,
the program retries with larger buffer sizes.
The following shell session shows a couple of sample runs:

SEE ALSO

COLOPHON

This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.